Purewell 3-Stage PW-OB
A low-priced, certified-filter 2.25 gal system for chlorine, taste and sediment. Fluoride needs a different model.
Amazon $145.99$145.99
The Purewell 3-Stage PW-OB is the better gravity water filter overall, rated 3.5 to 3.3. The Purewell 3-Stage PW-OB leads on value. The Purewell 3-Stage PW-OB costs $54 less ($145.99 vs $199.99).
Prices were last checked November 9, 2026. Product prices and availability are accurate as of that date and are subject to change; the price and availability shown on Amazon or the retailer's site at the time of purchase apply. As an Amazon Associate we earn from qualifying purchases.
Waterdrop TK-AB-FS
A cheaper way to get fluoride filters in the box than the TK-FS, with silver in the carbon filters.
Amazon $199.99$199.99
Which should you buy?
- Choose the Purewell 3-Stage PW-OB for value ($64.88 per gallon of capacity ($145.99, 2.2 gal) vs $88.88 per gallon of capacity ($199.99, 2.2 gal)).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every up to 2.25 gal gravity water filter; a clear win is highlighted. How we rank explains each one.
| Factor weight | Purewell 3-Stage PW-OB | Waterdrop TK-AB-FS |
|---|---|---|
| Overall rating | 3.5/5 | 3.3/5 |
| Value 25% | 84 $64.88 per gallon of capacity ($145.99, 2.2 gal) | 64 $88.88 per gallon of capacity ($199.99, 2.2 gal) |
| Running cost 15% | 74 $0.012 per gallon filtered ($36.99 per element, 3,000 gal each) | 50 replacement cost or element life not published (neutral score used) |
| Capacity 15% | 17 2.2 gal tank | 17 2.2 gal tank |
| Certification 20% | 40 states certification to NSF/ANSI 42, NSF/ANSI 372 | 40 states certification to NSF/ANSI 42, NSF/ANSI 372 |
| Element life 15% | 100 3,000 gal rated per element | 100 3,000 gal rated per element |
| Warranty 10% | 0 warranty not published, scored as none | 11 1-year warranty |
Specifications
| Purewell 3-Stage PW-OB | Waterdrop TK-AB-FS | |
|---|---|---|
| Capacity and flow | ||
| Tank capacity | 2.2 gal | 2.2 gal |
| Price per gallon of capacity | $64.88 | $88.88 |
| Elements included | 2 | 4 |
| Maximum elements | 2 | 4 |
| Flow, as shipped | 4 gal/hr | - |
| Filtration | ||
| Element type | Black carbon composite: 0.01 micron UF membrane, silver ion membrane and carbon block | Coconut shell carbon block with silver ions (black) |
| Certified | NSF/ANSI 42, NSF/ANSI 372 | NSF/ANSI 42, NSF/ANSI 372 |
| Certification detail | Listing: the black carbon filter passed NSF/ANSI 42 certification and the system passed NSF/ANSI 372. | Listing title: NSF/ANSI 42&372 Standard. The listing text does not say which component is certified. |
| Fluoride | - | Included |
| Fluoride element life | - | 1,000 gal |
| Running cost | ||
| Rated life per element | 3,000 gal each | 3,000 gal each |
| Replacement element | 37 $ | - |
| Cost per gallon filtered | $0.012 | - |
| Build | ||
| Material | 304 stainless steel | 304 stainless steel |
| Height | 20 in | - |
| Diameter | 8.9 in | - |
| Weight | 8.5 lb | - |
| Warranty | - | 1 year |